Apparatus for treating wood pulp



Sept. 6 1955 B. ARMSTRONG 2,716,926

APPARATUS FOR TREATING WOOD PULP Filed Jan. 2, 1951 G5 ll 4 8\ 72 |6o| I I g 57 72 58 l" 59 7 as q |6l 54% 2 f 5 28 a7 :2 5e 42 3 v Z 78 I I: fi

BRUCE ARMSTRONG 3r mentor (Ittorneg out United States Patent APPARATUS FOR TREATING WOOD PULP Bruce Armstrong, Saginaw, Mich., assignor to Jackson and Church Company, Saginaw, Mich., a corporation of Michigan Application January 2, 1951, Serial No. 204,039 8 Claims. (CI. 92-26) This invention relates to an apparatus for bleaching cellulosic fibers.

In the bleaching of wood pulp it has been the practice until comparatively recently to suspend the fibers in sufficient water to form a slurry containing from three to six per cent by weight, or even less, of actual fiber on a of actual fiber and the consequent large amount of equipment necessary for a moderate production of bleached fiber. The method is also characterized by the consumption of a relatively large amount of bleach per unit weight of fiber for a given degree of bleaching. This is thought to be due to the low actual concentration of bleach existing in the solution in which the fibers are suspended and, also, because considerable decomposition of the unused bleach occurs, particularly when peroxide bleaches are employed, during the long period of agitation of the pulp necessary to complete the process. Such decomposed bleaching agent is not available for useful bleaching. Elevation of the temperature of the slurry to increase the rate of bleaching increasees the rate of decomposition of the bleaching agent, the latter rate increasing faster than the former when more than moderately elevated temperatures are employed.

Certain of these difficulties can be overcome to some extent by using a modification of the low density bleaching process wherein a slurry containing from about ten to about fifteen per cent of fibers at from 80-120 F. is mixed with a suitable bleaching agent. This modification, originally referred to as a high density bleaching process is now often referred to in the art as a moderate density process. It is often possible in the operation of the moderate density process to use a somewhat higher bleaching temperature than in the case of low density bleaching and to complete the bleaching operation in from one to three hours. The process also has the advantage that considerably less water is used per unit weight of fiber than in the low density process with an attendant saving in equipment, steam and handling costs. It has been found that when using moderate density processes no sacrifice in brightness or yield of the finished pulp is incurred over the low density methods.

It has been proposed to increase further the proportion of fiber to water in an attempt to overcome the above and other difiiculties inherent in both the low density and the moderate density processes. Processes which have been proposed, and which have been employed to a limited extent, involve mixtures containing from twenty to thirty per cent by weight, or even slightly more, of fiber and are now frequently referred to as high density processes.

While such high density processes can be carried out with an increase in the overall efiiciency of utilization of the bleach, particularly when using sodium peroxide, hydrogen peroxide or other peroxide bleaches, and with the production in high yield of pulp having an excellent brightness, the use of such high ratios of fiber to water presents new difliculties not encountered in either the low density or moderate density methods. It is well known that wood pulp containing as little as forty per,

cent of actual fiber on a dry basis does not form a slurry which can be handled as a liquid and that it must be handled more as a solid would be handled. It can neither be pumped through a pipe nor stirred in a tank using conventional agitators. Slurries containing as little as twenty to thirty per cent of fibers are so thick that power requirements for agitating them are excessive. The difliculty of mixing a relatively small volume of one liquid evenly with a large volume of a thick or viscous liquid are well known and, in a high density process such as that just mentioned, the difficulties of securing even distribution of the bleach throughout the mass so that it contacts all of the fibers quickly and in the desired concentration in the water present are increased enormously as compared with the conventional low density method. It is thus difiicult and generally impractical to carry out the previously proposed high density bleaching processes without employing highly specialized and costly equipment and'the method is generally considered uneconomical. For these and other reasons, high density bleaching processes have not come into general use in spite of the advantages noted.

It has now been found, and is herein first disclosed, that wood pulp, which has a fiber content so high that there is substantially no water present in the liquid phase in the mass, i. e. in the interstices between the fibers, can be bleached conveniently, rapidly and economically and in continuous fashion using the hereinafter described method. Generally speaking, and depending to some extent upon the particular kind and grade of pulp employed, the method is particularly adapted to the bleaching of pulps containing from about 30 to about per cent or more of fibers on a dry basis. It is preferable for the best operation of the process that there be substantially no water present in the liquid phase in the pulp mass although in certain instances the presence in the mass of a small proportion of liquid phase water will not render the process entirely unworkable. The proportion of such liquid phase water should, however, be kept as low as possible, it being desirable if not essential that the solidliquid interfacial area within the mass be small as compared to the total interfacial area.

Pulps containing only a small proportion of moisture, e. g. from 5 to 10 per cent and even less, can be bleached readily using the method. It is to be noted that the method is thus particularly adapted to the bleaching of pulps having a consistency such that they cannot be bleached readily using any of the heretofore mentioned processes. In commercial practice the upper limit of fiber content of the pulp used in the process is generally more dependent upon preceding steps employed in preparing, processing and handling the pulp than upon the limitations of the process itself. It is often desirable for these reasons to use a pulp having a consistency of from about 35 to about 45 per cent, especially when bleaching is carried out in the same mill where the pulp is produced.

The process is, however, equally applicable to the bleaching of pulp having a higher consistency and can be operated with equally advantageous results on dry pulp containing as much as 90 per cent or more of fibers on a dry basis. When pulps of such high consistencies are used it is generally advantageous to submit them to a preliminary rough disintegrating action to provide fiber-separating zone with a bleaching agent in very finely 3- divided form. Gaseous bleaching agents can be used as such and liquid bleaching agents are atomized to form extremely small droplets. Solid bleaching agents can be dissolved in a suitable solvent to form a liquid agent.

In a preferred procedure, a liquid bleach is fed directly into the fiber-separating zone at an intermediate point such that the subsequent fiber-separating action and violent agitation of the fibers effects atomization of the bleach within the zone itself. The final fiber-separating zone should desirably be of such intensity and character that the fibrous product which issues from the zone consists substantially of separate individual fibers and the atomization of a liquid bleach should, for best results, be such that the individual dropletsare extremely small. Such separation of the fibers and atomization of the bleach, coupled with the violent agitation of the entire mass in the fiber-separating zone, particularly in the region thereof following the region in which the bleach is mixed with the fibers, causes the minute droplets of atomized bleach to contact instantly substantially the entire surface of each individual fiber.

It has been found that when the process is carried out in the preferred fashion, the liquid bleach being introduced into the fiber-separating zone at a distance sufificiently removed from the point of exit of the fibrous mass therefrom to provide ample time and agitation of the mass after the addition of the bleach for the latter to be sufficiently atomized and for the atomized bleach to contact thoroughly the surfaces of the individual fibers, a high efiiciency in the use of the bleach is obtained. It has also been found, quite unexpectedly, that the retention period of the pulp carrying the atomized bleach following its removal from the fiber-separating zone, e. g. in a retention chest, can often be shortened to as little as from about five minutes, or sometimes even less, to about one hour with the production of a bleached pulp equal to or better in brightness to that obtained using conventional low or moderate density procedures employing the same or a somewhat higher proportion of bleach to fiber and the same temperature and a retention period of from three to six hours or longer.

The process thus avoids the necessity of handling the large amounts of water inherent in both the low and moderate density methods. It yields a pulp having a brightness equal to or better than the best obtainable using low or moderate density methods and efiects a considerable saving in power and bleach as compared with these processes. Although the method is particularly useful in, and is described herein with particular reference to, the bleaching of wood pulp including ground-wood, sulfite, soda, kraft and semi-chemical pulps, it is equally useful in the bleaching of a wide variety of other cellulosic fibers, such as hemp, flax, cotton, bagasse, ramie and other fibers of vegetable origin.

It is to be noted that the conditions provided for contacting the fibers and bleach encountered in the herein described process differ materially from the conditions prevailing in the heretofore described processes. Due to the low moisture content and high fiber content of the pulp and to the violent agitation to which it is subjected in the fiber-separating zone, the mass approaches a state wherein the separated individual fibers each have a large proportion of their surfaces in contact with air, which permeates the mass thoroughly, rather than with water. Because of the high fiber content of the mass not only is there no appreciable liquid water phase between the fibers and no appreciable film of liquid water on the fiber surfaces, but the individual fibers are receptive to the absorption and adsorption of additional quantities of moisture.

Under these conditions it appears that the fibers possess an afiinity for minute droplets of an atomized liquid leach, or for a gaseous bleach, which it is not possible to take advantage of in conventional processes involving a continuous liquid phase surrounding the fibers. As a result of this afiinity, not only is the intimate contacting of the bleach with the fiber surfaces facilitated, but it may be that there is an actual and rapid penetration of bleach into the fiber itself. The violent agitation of the mass during and following the addition of the bleach contributes further to the even distribution of bleach throughout the mass, especially in the case of liquids, both by reason of dividing it mechanically into droplets or particles approaching colloidal dimensions and by dispersing the finely divided particles practically instantaneously and evenly throughout the substantially continuous air phase in the mass. There is little or no tendency for fibers in a certain part of the mass to become saturated. or soaked with a liquid bleach at the expense of fibers in other parts of the mass even though the liquid is run directly onto the agitated mass of fibers, the atomization and distribution of the liquid being effected so rapidly that the initial liquid does not have time to saturate the fibers with which it first comes into contact. Any droplets which may have a tendency to adhere to a fiber surface are immediately displaced or wiped along the surface by an adjoining fiber.

It is apparent that a further desirable feature of the process is that the combined fiber-separating and contacting operation be carried out in a manner such that the body of fibers being separated and contacted with the atomized bleach be in a thin layer to enable the individual fibers to be torn from one another. Care should be taken, of course, to prevent the fibers being unduly broken or sheared since the production of a large proportion of shortened fibers in the final product is generally disadvantageous.

It has been noticed, also, that optimum increase in brightness of the pulp per unit of available oxygen in the bleach is obtained when the process is carried out using pulp containing at least about 30 per cent by weight of fibers on a dry basis. When the process is carried out using less than about 30 per cent by weight of fibers, there is a marked decrease in efficiency of utilization of the bleach as measured by the points increase in brightness of the pulp obtained per unit of available oxygen. It may be that this decrease is related to a lowering in the absorption capacity of the fibers when the fiber content of the pulp is decreased to below about 30 per cent.

A particularly advantageous feature of the process is that it enables the fibers to be contacted with a more concentrated bleach than is possible using methods involving a suspension of the fibers in Water because the liquid bleach added contacts the fibers directly without dilution. It may even be that considerable evaporation of water from an aqueous bleach occurs during its atomization and that this actually effects a concentration of the bleaching solution within the mass of fibers. Regardless, however, of theory, it has been observed that when employing the process of the invention in the bleaching of a particular pulp with a particular bleaching agent, the amount of bleach per unit of pulp can usually be decreased by as much as 25 per cent or more as compared with the amount necessary when employing an aqueous suspension of the fibers, but without any sacrifice in brightness of the bleached fibers.

The process can be carried out over a considerable range of temperature. The actual temperature employed in a particular instance will depend to some extent upon the particular pulp and the particular bleach employed dim as well as upon other factor Temperatures sufficiently high to effect decomposition of .the bleaching agent should, of course, be avoided. It has been noted in some instances that more advantageous results are obtained employing a lower proportion of bleach per -unit weight of pulp and a lower temperature combined with a somewhat longer retention period following the contacting of the bleach and pulp than whena somewhat higher proportion of bleach is used at a somewhat higher temperature and the treated pulp retained for a somewhat shorter period of time. In many instances, however, the process is carried out at ambient temperatures Without either heating or cooling the pulp or the bleach. Satisfactory results have been obtained using temperatures of about 70 to about 140 degrees Fahrenheit, and a retention period of 30 minutes or somewhat longer. It is understood that the retention period depends to some extent upon the temperature at which the process is carried out and that when longer retention periods are not objectionable, e. g., by reason of necessary storage or shipping of the treated pulp prior to its use, the process can be carried out at substantially any convenient temperature lower than those mentioned. In most instances the pulp is conveyed, e. g., blown or transported in cars, directly from the apparatus in which the fibers are contacted with the bleach to the paper making or other manufacturing process in which it is to be used without the necessity of an intermediate specific storage capacity of any appreciable volume. It is understood, however, that the process is not limited in its broadest aspects as to temperature, proportion of bleach to pulp, the nature of the bleach employed or the length of time for which the treated pulp is retained before being processed further and that these factors can :be varied over relatively wide ranges, as desired, without departing from the spirit of the invention.

Insofar as is known, any bleach which can be used in the liquid or gaseous state for bleaching cellulosic fibers can be employed in the process. In commercial practice a liquid bleach is preferred because of greater ease of handling and storage. Particularly advantageous results have been obtained employing from about 1.0 to about 2.0 per cent aqueous hydrogen peroxide and the invention is herein described with particular reference thereto, it being understood, however, that any other convenient or conventional bleach can be used, such ,as gaseous chlorine, aqueous sodium peroxide, an aqueous hypochlorite and others. The proportion of bleaching agent to pulp is generally dependent upon factors such as the type of pulp employed, the particular bleaching agent used, degree of bleaching desired and others apparent to those familiar with the art. phasized, however, that using the process of the invention a saving of 25 per cent or more in the amount of a particular bleaching agent necessary to increase the brightness of a particular pulp by a given number of points can generally be effected as compared with the amount necessary to secure the same etfect using conventional low density and moderate density processes. The rates of supply of pulp and of bleach to the fiberseparating zone are regulated to give any desired proportion of bleach to pulp. Conventional agents, such as sodium silicate and other alkaline salts, sulfuric acid and the like, generally used in the art in conjunction with bleaching agents to adjust the pH of the pulp mass and otherwise to promote the most effective utilization of the bleaching agent, are also generally employed in the present process.

The process of the invention can be carried out using any suitable apparatus. In one convenient form .of apparatus the fiber-separating zone is formed by relatively closely spaced non-planar surfaces having a rapid relative movement which contribute not only to the separation of the fibers but also to the actual atomization of the bleach. As mentioned previously, a liquid bleach It should be emcan be fed directly at an intermediate point of such a zone onto a stream of pulp passing through the zone, the bleach being atomized instantly within the zone. One suitable apparatus is shown in the accompanying drawing wherein, in the interest of clarity, certain features are shown on a somewhat exaggerated scale and wherein:

Figure 1 is a sectional elevation of an apparatus useful in carrying out the process of the invention and including closely spaced members having non-planar surfaces, one of which is adapted for rapid movement relative to the other.

Figure 2 is a top plan view of a section of a non-planar surfaced member of the apparatus of Figure 1, and

Figure 3 is a sectional elevation of a section of Figure 2.

DESCRIPTION OF APPARATUS The apparatus illustrated in Figure 1 of the drawing includes a stationary housing functioning in part as a supporting frame and which, for ease in assembly, is preferably formed of a top section 11, an intermediate section 12 and a base section 13, the sections being secured together as by bolts 14 and 15 extending through suitable peripheral flanges formed on the housing sections. The central housing section 12 is formed with a transverse member 16 adjacent its upper end to provide a circular trough around a central port, the purpose of which will be apparent as the description proceeds. The top section 11 of the stationary housing is formed with a large central feed port 17 for introduction of pulp into the apparatus by any suitable and conventional feeding device, not shown. The underside of the top housing section 11 is suitably contoured to form an inverted circular trough around the port 17 in register with the circular trough in the transverse member 16 to provide a peripheral conduit through which pulp can be forwarded from within the apparatus to an exhaust port 18 at the side of the apparatus.

The transverse member 16 of the intermediate housing member 12 is further formed with a depending section 19 integral therewith prolonging the central bore. An additional, generally tubular, stationary member or annular ring, 22 is also provided which is secured as by bolts 23 to the underside of the transverse member 16 encircling the ..depending section 19. The lower end of the generally circular member 22 is provided with a centrally bored end plate 24 which is secured to the member 22 as by bolts 25 or in other convenient manner. The central bores of the member 19 and of the member 24 are formed to provide elongated bearing surfaces 26 and 27, respectively, on their inner surfaces.

An axially slidable, generally tubular, housing 29 is positioned within the central bores of the members 16, 19 and 24. The outer surface of the tubular housing 29 is provided with external bearing surfaces adjacent its upper and lower ends to bear on the bearing surfaces 26 and 27, respectively. Rotation of the housing 29 is prevented by means of a suitable key 34 lying in suitably formed registering slots formed in one of the bearing surfaces 26 and 27 and the corresponding external bearing surface on the member 29.

A central shaft 28 extends axially through the slidable housing 29 and is rotatably mounted therein as by means of bearings 32 and 33 adjacent each end of the housing, the shaft being secured against end play within the housing 29 in any convenient or conventional way, e. g. by a collar 61 integral near the upper end of the shaft and integral therewith and a lock collar adapted to be secured to the shaft below the lower bearing 33. The central shaft 28 is equipped at its lower end with a pulley 78 or other suitable means by which it can be rotated from a power source, not shown.

Suitable means are provided for adjusting accurately the vertical position of the slidable housing 29 with respect to the bearing surfaces 26 and 27 and for holding it firmly in this position following the adjustment. One such suitable means characterized by a high degree of accuracy and fineness of adjustment includes a tubular non-rotatable elevator screw 35 encircling the slidable housing 29 intermediate the bearing surfaces 26 and 27.

In a preferred embodiment, an annular elevator screw 35 has an internally directed flange 37 at its lower end and is provided with external screw threads of rectangular cross-section. This elevator screw is encircled and its threads engaged by the internally threaded, annular, elevating sleeve 46. This latter is free to rotate with respect to the frame of the machine but is held axially by the top flange 47 and the worm wheel 49 (to which latter it is attached by cap screw 52) snugly engaging the annular stationary ring 48 which is formed on the inner side of the housing member 22.

Pins 36 extending downwardly from the annular member 19 engage corresponding openings in the top flange of elevator screw 35 and prevents rotation of said elevator screw with respect to the frame of the machine but permits axial movement with respect thereto.

A heavy coil spring 3 encircles the elevator screw 35, rests on the flange 37 and exerts pressure against the shoulder 38 of the member 29, which latter is free to slide axially within depending section 19. The normal operating position of the member 29, and the parts supported thereby, is determined and limited in a downward direction by the strength of said spring 39 and in an upward direction by an adjustable collar 42 which is held in position by the set screw 43. Thus, the member 29, together with the shaft, shaft bearings and the disk 57, continually float on the spring 39. In the event tramp metal or other hard, foreign object, should enter into the machine with the pulp, the spring 39 will yield and permit the disks to separate sufliciently to pass said object therebetween without damaging the teeth thereof, the hearings, or other parts. When the foreign object has passed, the disks will return to their original position.

Bearing surfaces 53 and 54 are provided on the outer surface of the elevating sleeve 46 between the flange 47 and the worm wheel 49 and on the inner surface of the inwardly extending ring member 48 to maintain the elevator screw 35 and elevating sleeve 46 in an accurately centered position.

Rotation of the elevating sleeve 46 is effected as desired by means of a worm 55 meshing with the teeth of the worm wheel 49, the worm 55 being secured to a horizontal shaft 56 which extends through the outer housing 13 of the apparatus and is equipped at its outer end with a hand wheel, not shown. Adjustment of the central shaft 28 in an upward or downward direction is thus effected with ease and with great precision by rotation of said hand wheel. At the same time, any vibration and movement of the central shaft 28 out of accurate alignment is prevented by the heavy and elongated bearing surfaces 26 and 27 in which the slidable housing 29 slides, so that the fine adjustment of the central shaft 28 is not destroyed at high speeds of rotation under heavy load.

A heavy horizontal rotor plate 57 is keyed, as by a key 60, on the upper end of the central shaft 28 in abutment on its lower side with a collar 61 integral with the shaft. A cover plate 58, centrally bored to accommodate the collar 61, is secured as by bolts 59 on the top end of the slidable housing 29 effectively preventing the entry of water, dirt or other foreign matter into the housing 29 and the bearings 32 and 33 therein. A cap cone 62 is secured to the upper end of the central shaft 28 as by a bolt 63 to hold the rotor plate 57 firmly against the collar 61 and is formed on its top surface to provide a smooth outwardly and downwardly sloping surface along which pulp introduced into the apparatus through the port 17 can slide without retardation. A series of vanes 64, usually two to five in number, are on the cap cone 62 and serve, upon rotation of the central shaft 28, the plate attached thereto and its accompanying cap cone 62, to for- 8 ward pulp radially outwardly to enter between the upper surface of the plate 57 and the lower surface of the housing member 11. A series of fins or paddles 65 are secured around the periphery of the plate 57 which convey the so-forwarded pulp to the discharge port 18 and discharge it from the machine.

The outer section of the upper surface of the rotor plate 57 is formed to receive a shredder plate 66 which is secured thereto as by a series of bolts 67. The inner or under surface of the upper housing member 11 is similarly formed to receive a second or upper shredder plate 68 which is secured thereto as by bolts 69 in a position facing the lower shredder plate 66. The upper shredder plate is thus stationary while the lower shredder plate is rotatable.

The facing surfaces of the shredder plates 66 and 68 converge radially outwardly and are provided with a series of teeth or impacting elements 72 as shown more clearly in Figures 2 and 3. Each tooth or impacting element on the lower shredder plate is formed with its leading face vertical and substantially in the form of an isosceles triangle having a horizontal base. The lateral surface of each of the impacting elements is preferably normal to its leading face for a short distance rearwardly therefrom to provide a sturdy plate and each plate is rigidly braced by projecting each of its trailing edges inwardly and backwardly to a point substantially in a plane including the base of the isosceles triangle and normal to the leading face of the element.

The impacting elements are formed in rows each lying on an arc of rotation of the rotor plate 57 and each tooth in each row having substantially the same dimensions. The teeth in each successive row are smaller in each of their dimensions, and lie closer together in the row than the teeth in the next adjacent row nearer the center of rotation of the rotor plate 57. In certain of the outer rows the vertical leading face of one element often inter sects the trailing section of the tooth next forward in the same row. The rows of teeth are, furthermore, located closer together as the size of the teeth in the rows becomes smaller so that there are formed a series of circular grooves of triangular cross section lying between the rows of teeth, each groove being smaller in depth and top width than the next adjacent row inward toward the center of rotation. The number of teeth in the innermost row is selected to permit sufiicient space therebetween to allow the pulp pieces to enter. The ratio of the number of teeth in all the other rows with respect to the number of teeth in each respective next inner row is approximately \/2/ I.

The impacting elements carried by the upper, stationary shredder plate 68 are formed in substantially the same manner as the elements on the lower shredder plate just described and are located so that each row projects into a groove between adjoining rows of elements on the lower shredder plate. They are further formed with their vertical faces facing the vertical faces of the teeth on the lower shredder plate. In addition, the impacting elements 72 on the upper and lower shredder plates are positioned vertically in such fashion that the clearance between impacting elements on the two shredder plates as the lower plate is rotated is greatest at the inner edges of the plates where the elements are largest, the clearance for any vertical setting of the lower plate decreasing regularly outward along the radii of rotation to a value 6 which is frequently only a few thousandths of an inch.

This provides a zone wherein, as pulp is fed to the apparatus through the central feed port 17 and impelled outward by centrifugal action and the vanes 64, the pulp is subjected to a mechanical fiber-separating action of progressively increasing intensity due to the greater number of elements in the peripheral rows and to the graduation in size and clearance of the two sets of impacting elements and, also, to the fact that the outer elements pass one another at a higher rate of speed than do the inner, larger elements due to their greater distance from the center of rotation.

-\ NA E nnsclurrrou OF METHOD In the operation of the apparatus shown in the drawing, whereby the new method is practiced, the raw pulp which is to be bleached is fed into the apparatus through the feed port 17 with the rotor plate 57 and the attached lower shredder plate 66 rotating at a high speed. The pulp is immediately forwarded by the rotating vanes 64 outwardly along the top surfaces of the conecap 62 and the rotor plate 57 and is conveyed by centrifugal action and by .he action of the impact elements 72 on the upper and I n61 shredder plates 68 and 66 through the fiberseparating zone between the shredder plates. The pulp is thus subjected in this zone to fiber-separating action caused by the rapid passage of .the impact elements on the rotating lower shredder plate past the impact elements on the stationary upper shredder plate. The fiber-separating action increases in its intensity as the pulp moves outward through the fiber-separating zone due .to the progressively d c sed sp c n bet een oppo d s faces of the plates, to closer tolerance between the two sets of impact elements, and to the smaller size and greater number and relative speed of the elements encountered by the pulp as it passes through the zone. Following its passage through the zone, it emerges from between the shredder plates and is impelled by means of the blades 65 through the circular channel in which the blades travel and is subsequently discharged from the machine through the discharge port 18.

The bleaching agent, preferably in liquid form, is introduced into the pulp mass during its passage through the fiber-separating zone, preferably at a point sulfieiently far removed from the end of the zone to provide for adequate atomization and distribution of the atomized solution through the pulp before it emerges from the fiber-separating zone. One convenient way of introducing a liquid bleach into contact with pulp within the fiber-separating zone includes a feed pipe or conduit 75 which projects downward through a port in the upper housing member 11 and is threaded at its lower end to engage an internally threaded port in the upper shredder plate 68, the solution being fed through the conduit at a desired rate from a convenient storage and regulating means, not shown. The conduit may be located between theoretical circles concentric with the fixed disk of which one is located about mid-way betwen the inner and outer edges of the said fixed disk and the other is located about two-thirds of the distance betwen said edges. In practice, it has been found convenient to introduce the bleaching agent into contact with the violently agitated pulp at 3 equidistant points approximately two-thirds of the distance through the fiber-separating zone measured from the point of entry of the pulp into the zone. Alternatively, a plurality of feed-pipes can be employed for introducing the bleach into the fiber-separating zone at other suitably spaced intervals. 7

Certain advantages are apparent from the following examples which are given by way of illustration only, and are not to be considered as limiting, it being understood that the composition of the bleach, the temperature of operation, the proportion of bleach to fiber and other factors will usually be adjusted within the limits given depending upon the particular pulp being bleached and the degree and rapidity of bleaching required.

Example 1 In a typical instance of the operation of the process, an apparatus similar to that described in the previous paragraphs was employed. The row of largest teeth consisted of 18 teeth each inch high with its apex 8 inches from the center of rotation. The outermost row consisted of 372 teeth each 0.379 inch high with the apex of each 13 inches from the center of rotation. The lower shredder plate --was rotated at a speed .of 1750 R. P. M. with a-maximum clearance of approximately inch .ofihe largest teeth at the inner edge .of the shredder plates decreasing regularly to a minimum clearance .of approximately ,5 inch of the smallest teeth at the .outer edge of the shredder plates.

Ground wood pulp consisting of approximately 10 per cent spruce and per cent poplar containing 40 percent of fibers on a dry basis was fed continuously into the machine at the rate of 1.25 (0.5 ton bone dry fiber) tons per hour. A bleaching solution was prepared by mixing 7080 pounds of water, 270 pounds of 50 per cent aqueous hydrogen peroxide and 1000 pounds of sodium silicate solution (12 per cent NazO). The bleaching solution, which contained 1.62 per cent actual hydrogen peroxide (3.24 per cent of 50 per cent strength) was fed into the fiber-separating zone of the machine into contact with the pulp passing therethrough at a point about two-thirds of the way through the zone with respect to the direction of flow of the pulp at the rate, of 50 gallons (417 lb.) of solution per hour. The temperature of both the pulp and the bleaching solution was about 75 degrees Fahrenheit.

The pulp issuing from the fiber-separating zone had a fiber content of 34.4 per cent on a dry .basis and a pH between 9.5 and 10. The pulp was packaged immediately for storage. Samples were taken directly from the pulp issuing from the machine from time to time and its bright ness determined using the General Electric Reflectance Meter. Samples taken directly from the machine had a brightness as determined using a General Electric Refiectance Meter 8 to 12 points higher than the unbleached pulp.

Specimen packages of the bleached pulp were opened from time to time and the brightness of the pulp determined. It was found that the brightness increased continuously and appreciably during storage but at a decreasing rate, reaching an average maximum increase of about 16 points after about three days. At the end of three days the pH of the pulp was about 6.8. Samples of the bleached pulp examined after about three months indicated that no reversion in brightness occurred on long storage.

Example 2 Ground wood pulp consisting of a mixture of approximately 60 per cent poplar, 30 per cent spruce and 10 per cent balsam'and containing 38 per cent of fibers on a dry basis was fed continuously into the machine used in Example 1. A bleaching solution was prepared by mixing in the order given 46228 pounds of water, one pound of magnesium sulfate, 1000 pounds of sodium silicate solution (12 per cent N320), 191 pounds of 50 per cent aqueous hydrogen peroxide and 175 pounds of sodium peroxide. The bleaching solution thus prepared was fed into contact with the pulp passing through the fiber-separating zone of the machine'as before at the rate of 570 gallons (4760 pounds) per ton of fibers calculated on a bone dry basis. The temperature of both the pulp and bleaching solution was about degrees Fahrenheit. The pulp issuing from the fiber-separating zone had a pH between 9.5 and 10. An increase in brightness of the pulp comparable to that of Example 1 was obtained.

It should be mentioned in connection with the operation of the apparatus shown in the drawing that it has been observed that when the machine is operated as described not only are the fibers of the wood separated completely from one another into substantially individual fibers, but also the pulp is deshived to a much greater degree than it has hitherto been possible to accomplish. At the same time it appears that the individual fibers are not broken unduly, as evidenced by photo-micrographs and screen classification tests.

Furthermore, and unexpectedly, it has been observed that when the machine is adjusted to provide only a very small clearance, e. g. inch or less, at the outer edge of the fiber-separating zone the pulp is fibrillated and the fibers are curled to such an extent that they can be felted readily. The degree of fibrillation and curlation of the fibers which can be obtained readily in this way appears to be greater than that obtained heretofore and the so modified fibers appear to have utility not hitherto suspected of wood fibers.

I claim:

1. A machine for disintegrating fibrous cellulosic material and simultaneously contacting same with a fluid treating agent, comprising the combination: a frame, a central shaft rotatably supported by said frame, and means effecting rotation of said shaft; a toothed rotating disk, having axially extending, circumferentially and radially spaced, teeth, affixed to one end of said shaft, said teeth being on the side of said disk opposite to the shaft; a fixed annular disk opposing said rotating disk and being of the same outside diameter as said rotating disk, said fixed disk having axially extending, circumferentially and radially spaced teeth extending toward said rotating disk and overlapping the teeth thereof; a housing surrounding both of said disks, said housing having cen trally located means defining a feeding entrance through the center of said fixed disk and having also peripherally located ofitake means; and conduit means extending through said housing and through said fixed disk at a point on said fixed disk between, and only between, theoretical circles concentric with said disk of which one is located about midway between the inner and outer edges of said fixed disk and the other is located radially outwardly from said first circle about two-thirds of the distance between said edges; whereby fluid treating agent introduced through said conduit will be immediately atomized by said teeth and thoroughly mixed with said fibrous material simultaneously with disintegration of said fibrous material substantially to its elemental fibers.

2. In a device for disintegrating fibrous material and simultaneously contacting the surfaces of the fibers thereof with a treating fluid, and including a fixed upper disk and a rotating lower disk, the improvement comprising: a supporting frame; a vertically disposed shaft; a tubular member surrounding said shaft, supporting same rotatably with respect thereto and holding said shaft against relative axial movement with respect thereto, said tubular member having an external, circumferential, downwardly facing shoulder near its upper end; a pair of spaced, elongated, vertically aligned and concentric bearings supporting said tubular member for. axial movement with respect to said frame, said shoulder being positioned immediately below the uppermost of said bearings; an annular ring supported by said supporting frame, concentric with said shaft and axially positioned between said bearings; an elevating sleeve rotatably supported on said annular ring and having internal threading; an annular elevator screw having external threading engaging the threading of said elevating sleeve and supported thereby, an internally extending annular flange at the lower end of said elevator screw; means on said tubular member engaging said elevator screw for preventing relative rotative movement therebetween but permitting axial movement therebetween; a coil spring surrounding said tubular member, resting on said annular flange and bearing against said shoulder for resiliently urging said tubular member upwardly; a worm wheel surrounding said tubular member and affixed to said elevating sleeve for rotation therewith; a worm and means supporting same in operative engagement with said worm wheel; manually operable means for rotating said worm.

3. In a device for disintegrating fibrous material and simultaneously contacting the surfaces of the fibers thereof with a treating fluid, and including a fixed upper disk and a rotating lower disk, the improvement comprising: a supporting frame; a vertically disposed shaft; a tubular member surrounding said shaft, supporting same rotatably with respect thereto and holding said shaft against relative axial movement with respect thereto, said tubular member having an external, circumferential, downwardly facing shoulder near its upper end; a pair of spaced, elongated, vertically aligned and concentric bearings supporting said tubular member for axial movement with respect to said frame, said shoulder being positioned immediately below the uppermost of said bearings; an annular ring supported by said supporting frame, concentric with said shaft and axially positioned between said bearings; an elevating sleeve rotatably supported on said annular ring and having internal threading; an annular elevator screw having external threading engaging the threading of said elevating sleeve and supported thereby, an internally extending annular flange at the lower end of said elevator screw; means on said tubular member engaging said elevator screw for preventing relative rotative movement therebetween but permitting axial movement therebetween; resilient means resting on said annular flange and bearing against said shoulder for resiliently urging said tubular member upwardly; and manually operable means for rotating said elevating sleeve.

4. A machine for contacting a fibrous cellulosic material with a fluid treating agent, comprising the combination: a supporting frame; a vertically positioned shaft and means rotatably supporting same on said frame'and means effecting rotation of said shaft; a toothed rotating disk having axially extending, circumferentially and radially spaced, teeth, said teeth being also aligned in circumferential rows and having blunt faces on the sides thereof leading in the direction of rotation of said disk with the number of teeth in any row after the innermost being approximately the number in the next adjacent innermost row multiplied by the factor /2, said disk being affixed to the upper end of said shaft and said teeth being on the upper side of said disk; a fixed annular disk of the same outside diameter as said rotating disk positioned for opposing said rotating disk and having similar axially extending, circumferentially and radially spaced, teeth, said teeth being also aligned in circumferential rows and positioned for extending toward said rotating disk and inter-meshing with the said teeth extending upwardly from said rotating disk; a housing surrounding both of said disks, said housing having centrally located means aligned with the opening in said fixed annular disk for providing a feeding entrance through said housing and annular disk to a point intermediate said annular disk and said rotating disk, and said housing having also peripherally located off-take means; and a conduit extending through said housing and through said fixed annular disk at a point on said fixed annular disk between, and only between, theoretical circles concentric with said disk of which one is located about mid-way between the inner and outer edges of said fixed annular disk and the other is located radially outwardly therefrom about two-thirds the distance between said edges; whereby a fluid treating agent introduced into said conduit will be immediately atomized by said teeth and caused thoroughly to contact the fibers of said fibrous material. I

5. A machine for contacting a fibrouscellulosic material with a fluid treating agent, comprising the combination: a supporting frame; a vertically positioned shaft and means rotatably supporting same on said frame and means effecting rotation of said shaft; a toothed rotating disk having axially extending, circumferentially and radially spaced, teeth, said teeth being also aligned in circumferential rows and having blunt faces on the sides thereof leading in the direction of rotation of said disk, and said teeth being of progressively smaller size and arranged in progressively greater numbers from the radially innermost to the radially outermost thereof, said disk being aflixed to the upper end of said shaft and said teeth being on the upper side of said disk; a fixed annular disk of the same outside diameter as said rotating disk positioned for opposing said rotating disk and having teeth of simi larly shape and size to those on said rotating disk, said teeth being axially extending, circumferentially and radially spaced, and being also aligned in circumferential rows and positioned for extending toward said rotating disk and inter-meshing with the said teeth extending upwardly from said rotating disk; a housing surrounding both of said disks, said housing having centrally located means aligned with the opening in said fixed annular disk for providing a feeding entrance through said housing and annular disk to a point intermediate said annular disk and said rotating disk, and said housing having also peripherally located off-take means; and a conduit extending through said housing and through said fixed annular disk at a point on said fixed annular disk between theoretical circles concentric with said disk of which one is located about mid-way between the inner and outer edges of said fixed annular disk and the other is located radially outwardly therefrom about two-thirds the distance between, and only between, said edges; whereby a fluid treating agent introduced into said conduit will be immediately atomized by said teeth and caused thoroughly to contact the fibers of said fibrous material.

6. A machine for distintegrating fibrous cellulosic material and simultaneously contacting same with a fluid treating agent, comprising the combination: a supporting frame; a vertically positioned shaft and means rotatably supporting same on said frame and means effecting rotation of said shaft; a toothed rotating disk having axially extending, circumferentially and radially spaced teeth, said teeth being also aligned in circumferential rows, the number of teeth in any row after the innermost being approximately the number in the next adjacent innermost row multiplied by the factor V2, said disk being aflixed to one end of said shaft with the teeth being on the side of said disk opposite to said shaft; a fixed annular disk of the same outside diameter as said rotating disk positioned for opposing said rotating disk and having similar axially extending, circumferentially and radially spaced teeth, said teeth being also aligned in circumferential rows and positioned for extending toward said rotating disk and intermeshing with the said teeth on said rotating disk; a housing surrounding both of said disks, said housing having centrally located means defining a feeding entrance through the center of said fixed disk, said housing having also peripherally located off take means; conduit means extending through said housing and through said fixed disk at a point on said fixed disk between and only between theoretical circles concentric with said disk of which one is located about mid-way between the inner and outer edges of said fixed disk and the other is located radially outwardly therefrom about two-thirds of the distance between said edges; whereby fluid treating agent introduced through said conduit will be immediately atomized by said teeth and thoroughly mixed with said fibrous material simultaneously with disintegration of said fibrous material substantially to its elemental fibers.

7. A machine for disintegrating fibrous cellulosic material and simultaneously contacting same with a fluid treating agent, comprising the combination: a supporting frame; a central shaft and means rotatably supporting same on said frame and means eflecting rotation of said shaft; a toothed rotating disk having axially extending, circumferentially and radially spaced teeth, said teeth being also al1gned in circumferential rows, said teeth being of progressively smaller size and arranged in progressively greater numbers from the radially innermost to the radially outermost row thereof, said disk being afiixed to one end of said shaft with the teeth being on the side of said disk opposite to said shaft; a fixed annular disk of the same outside diameter as said rotating disk positioned for opposing said rotating disk and having similar axially extending, circumferentially and radially spaced teeth, said teeth being also aligned in circumferential rows and positioned for extending toward said rotating disk and intermeshing with the said teeth on said rotating disk; a housing surrounding both of said disks, Said housing having centrally located means defining a feeding entrance through the center of said fixed disk, said housing having also peripherally located off take means; conduit means extending through said housing and through said fixed disk at a point on said fixed disk between and only between theoretical circles concentric with said disk of which one is located about mid-way between the inner and outer edges of said fixed disk and the other is located radially outwardly therefrom about two-thirds of the distance between said edges; whereby fluid treating agent introduced through said conduit will be immediately atomized by said teeth and thoroughly mixed with said fibrous material simultaneously with disintegration of said fibrous material substantially to its elemental fibers.

8. A machine for disintegrating fibrous cellulosic material and simultaneously contacting same with a fluid treating agent, comprising the combination: a supporting frame; a central shaft and means rotatably supporting same on said frame and means effecting rotation of said shaft; a toothed rotating disk having axially extending circumferentially and radially spaced teeth, said teeth being also aligned in circumferential rows, said teeth being of progressively smaller size and arranged in progressively greater numbers from the radially innermost to the radially outermost row thereof, said disk being aflixed to one end of said shaft with the teeth being on the side of the disk opposite to said shaft; a fixed annular disk of the same outside diameter as said rotating disk positioned for opposing said rotating disk and having similar axially extending, circumferentially and radially spaced teeth, said teeth being also aligned in circumferential rows and positioned for extending toward said rotating disk and intermeshing with the said teeth on said rotating disk; a housing surrounding both of said disks, said housing having centrally located means defining a feeding entrance through the center of said fixed disk, said housing having also peripherally located off-take means; conduit means extending through said housing and through said fixed disk at a point on said fixed disk between and only between theoretical circles concentric with said disk of which one circle is located about mid-way between the inner and outer edges of said fixed disk and the other circle is located radially outwardly of said one circle and is sufficiently spaced from the outer edge of said fixed disk to provide for adequate atomization and distribution of the atomized agent through the material before it emerges from between said disks whereby fluid treating agent introduced through said conduit will be immediately atomized by said teeth and thoroughly mixed with said fibrous material.

References Cited in the file of this patent UNITED STATES PATENTS 80,171 Hartsock July 21, 1868 1,685,115 Adams Sept. 25, 1928 1,984,869 Farley et al Dec. 18, 1934 2,119,768 Anthony June 7, 1938 2,265,622 Basler Dec. 9, 1941 2,413,583 Shearer Dec. 31, 1946 2,471,043 Schenck May 24, 1949 2,516,384 Hill et al July 25, 1950 2,599,543 Coghill et a1 June 10, 1952 2,653,770 Vicci Sept. 29, 1953 FOREIGN PATENTS 60,913 Austria Aug. 25, 1913 373,691 Italy Aug. 1, 1939 714,304 Germany Nov. 26, 1941 951,064 France Oct. 14, 1949 603,679 Great Britain June 21, 1948 

1. IN A DEVICE FOR DISINTEGRATING FIBROUS MATERIAL AND SIMULTANEOUSLY CONTACTING THE SURFACES OF THE FIBERS THEREOF WITH A TREATING FLUID, AND INCLUDING A FIXED UPPER DISK AND A ROTATING LOWER DISK, THE IMPROVEMENT COMPRISING: A SUPPORTING FRAME; A VERTICALLY DISPOSED SHAFT; A TUBULAR MEMBER SURROUNDING SAID SHAFT, SUPPORTING SAME ROTATABLY WITH RESPECT THERETO AND HOLDING SAID SHAFT AGAINST RELATIVE AXIAL MOVEMENT WITH RESPECT THERETO, SAID TUBULAR MEMBER HAVING AN EXTERNAL, CIRCUMFERENTIAL, DOWNWARDLY FACING SHOULDER NEAR ITS UPPER END; A PAIR OF SPACED ELONGATED, VERTICALLY ALIGNED AND CONCENTRIC BEARINGS SUPPORTING SAID TUBULAR MEMBER FOR AXIAL MOVEMENT WITH RESPECT TO SAID FRAME, SAID SHOULDER BEING POSITIONED IMMEDIATELY BELOW THE UPPERMOST OF SAID BEARINGS; AN ANNULAR RING SUPPORTED BY SAID SUPPORTING FRAME, CONCENTRIC WITH SAID SHAFT AND AXIALLY POSITIONED BETWEEN SAID BEARINGS; AN ELEVATING SLEEVE ROTATABLY SUPPORTED ON SAID ANNULAR RING AND HAVING INTERNAL THREADING; AN ANNULAR ELEVATOR SCREW HAVING EXTERNAL THREADING ENGAGING THE THREADING OF SAID ELEVATING SLEEVE AND SUPPORTED THEREBY, AN INTERNALLY EXTENDING ANNULAR FLANGE AT THE LOWER END OF SAID ELEVATED SCREW; MEANS ON SAID TUBULAR MEMBER ENGAGING SAID ELEVATOR SCREW FOR PREVENTING RELATIVE ROTATIVE MOVEMENT THEREBETWEEN BUT PERMITTING AXIAL MOVEMENT THEREBETWEEN; A COIL SPRING SURROUNDING SAID TUBULAR MEMBER, RESTING ON SAID ANNULAR FLANGE AND BEARING AGAINST SAID SHOULDER FOR RESILIENTLY URGING SAID TUBULAR MEMBER UPWARDLY; A WORM WHEEL SURROUNDING SAID TUBULAR MEMBER AND AFFIXED TO SAID ELEVATING SLEEVE FOR ROTATION THEREWITH; A WORM AND MEANS SUPPORTING SAME IN OPERATIVE ENGAGEMENT WITH SAID WORM WHEEL; MANUALLY OPERABLE MEANS FOR ROTATING SAID WORM. 